The present invention relates to a capacitor of an MIM (Metal-Insulator-Metal) structure, more specifically a capacitor which can prevent peeling at the interface between the electrode and the capacitor dielectric film and deterioration of capacitor characteristics due to thermal processing and a method for fabricating the capacitor, and a method for fabricating a semiconductor device including such the capacitor.
DRAM is a semiconductor memory device which can be constituted by one transistor and one capacitor, and have been studied in structures and methods for fabricating semiconductor memory devices of high density and high integration. Especially areas occupied by capacitors much influence integration of devices, so that it is very important how to increase a capacitance per a unit area. To this end, for DRAM of giga-bit storage capacities, which have been recently developed, it has been studied in order to decrease areas occupied by the capacitors that the capacitor dielectric film is formed of metal oxide, whose dielectric constant is higher than those of silicon oxide film and silicon nitride film, which have been conventionally widely used. As such oxide dielectric films, oxide dielectric film, such as tantalum oxide film, BSTO film, STO film, PZT film, etc., have been studied.
Such oxide dielectric films as the capacitor dielectric film have been usually formed by CVD method. This is because the films formed by CVD method have high dielectric constants, low leakage current, and good step coverage. As electrode materials, noble metal material as of ruthenium (Ru) have been used. This is because noble metal films have good adhesion to oxide dielectric films and can form capacitors having large work function difference and low leakage current.
However, the inventors of the present application made various studies and have found that when an upper electrode is formed of a metal material on the oxide dielectric film, peeling at the interface between the oxide dielectric film and the upper electrode takes place due to later thermal processing.
In the usual semiconductor process, thermal processing after the uppermost passivation film has been formed is performed in a forming gas atmosphere for improving transistor characteristics. However, this thermal processing has often degraded electric characteristics of the capacitor.